Sound reproducer



Oct. 17, 1933;. E, H SMYTHE 1,930,912

SOUND REPRODUCER Filed Aug. 17 1926 a W ju/ Mme Patented Oct. 17, 1933 va A 9 2 Western Electric Company, Incorporated, New York, N. Y., a-corporation ofgNew York I Applican 's ugust 17,1926. s rial no. 129,734l n v fzo Claims. (01.1'81-31) V This invention relates to reproizlucerssoundreproducer having a modified form of pe-H employing largedirectractingdiaphragms. ripheral' support and havinga partiallyenclosed An object of the invention is to reproduce air chamber on bothsides of the diaphragm; efiiciently and faithfully all sounds within theFig.5 is a partial cross-sectional view showing I 5 audible range. r p f'1 f a modification of the double air chamber con 60,.

Another object of the invention isto increase struction. V j the energyimparted to the air from a sound, Thev sound reproducer shown-in Fig. 1comradiating surface and to'reduce the radiation prises a radiatorhaving a front conical diaof out of phase energy, -I phragm anda rearfrusto-conical section ll 10 The invention provides a sound 'reproducercemented together base to baset Both portions es having a transverselyrigid and preferablyconiofthe radiator are preferably constructed of caldiaphragm and an annular transversely rigid light stifi material, suchas thin wood veneer or and preferably frusto-conical section which areblotting paper. An annular binding strip 12 is supported solely at theircommon periphery in; disposed about the truncated end of the frusto-' 15such a way that the periphery is constrained conical section 11- forapurpose hereinafter de- 70. with respectto transverse movement and: isleft scribed. 7 H a a free and unconstrained with respect to radialTheradiator is mounted within an annular and torsionalmovement. V ftrough-like framel3 preferably comprising two Low frequency soundvibrations appliedatfthe semi-circular portions which may be clampedapex of the diaphragm..cause the periphery to togetherby means of boltsl4 after the radiator 75, expand and contract permitting the entiresuris placed inside the-frame. Theidevice ismount face of the diaphragmto vib'rate ina direction ed; on a stand 15 havinglan upright portion16. transverse to the plane of its base, andproducing to which arebolted diametrically opposite edge; a transverse movementof thefrusto-conical secof theframe l3. 7 I f r tion in opposite direction tothe transverse move- ;"I he cones 10 and ll are supported at their so,ment of the diaphragm, As aresult of this accommon periphery by means oftautcords -17; tion, the soundwaves transmitted by the outer passingthrough-the small holes 18 in thede surface .of the frusto-com'calsection'are in phase pending rims of the frame 13,. V The; cords 1 7 maywith the waves-of corresponding frequencies be laccd backandforth th h 31 9 51 30 transmitted by the outer surface of th'e conical as; is m reimarl shown in Eigs 2 and t 85H,

40 serves to improve the radiationof energvin the H.,C-. Ha1 rison.-

diaphragm, and the er surfaces of 5 these commonperipheral edge of thecones being asmembers cooperate to'produce, sound, waves: in tenedto.the cords by means of cement l9, A.

phase opposite tothat of ,thewavesprodu d'by supporting member 20mounted on the upright the outer surfaces, .1 f a v 1 I 35 Accordingtoanother feature of; the invention, ,diaphragm 10. The member 22 isprovided for '90. a partially enclosed air chamberis provided onconnecting the driving stem of the receiver unit each side of theconical diaphragm; The-col to the apex of thediaphragm. Thereceiverunitumns ofair confined in each air chamber add 2l maybeof the typedisclosedand claimed air mass reactance to the diaphragm, which U. S.Batent1,709,571,;granted April 16, 1929 tolow frequency range; f i 1,".In'theqconstruction described above the pe- The inventionswill bedescribed indetailin ripheryj oftthe-double cone structure isconconnection with the accompanying drawing, in strained in a transversedirectionby means ofthe which similar reference characters designate;cords 17-, hut;is left free to move radially and similar parts in the,difierent 1 views, and in tqrsionally. This construction reduces theoppo- 10o which:

Fig. l is a side. viewppartly in section, of a forces intl'ieiront andrear cones and'givesfree sound reproducer comprising a..double coneplay;to]any-;-tendency toward peripheral exparnstructure supportedat theperiphery in accordsionand contractionatthe periphery as the dia-f ancewith the invention; 3 1 p H I I a Fig. 2 'isa front elevation on areduced scale; and contracts radially,andneripherally-as a reof thesound reproducer showninFig- 1; Y 7 .sultpf the drivingforceappliedatthe apex this] 7 Fig. 3 is afragmentary: view illustratingthe. expansion and contraction produce a transverse, method ofsupportingthe double cone structure; movementi of the rear frusto-conicalsection:11; r

Fig. 4 is. aside view, partly in sectiom offa inopposite direction tothetransversemovemont very light gauge 2 of the conical diaphragm 10.Pressure waves which are produced by the frusto-conical section 11 aretherefore in phase with the waves of corresponding frequencies producedby the diaphragm 10. This particular action occurs in the low frequencyrange where it increases and emphasizes the pulsating, or pumping actionin the enclosed air space between the front and rear cones. This has theeffect of increasing the air transformer action and the effective airmass reactance upon the rear surface of the diaphragm 10 and improvingthe response in the low frequency part of the scale.

The truncated end of the frusto-conical section 11 is left unsupportedand free to vibrate, the sole support being at the common peripheraledge of the double cone structure. The binding strip 12 disposed aroundthetruncated edge of the frusto-conical section 11 is primarily to givecircular rigidity, and to provide stiffening of the inneredge to resistthe radially inwardly and I outwardly moving forces caused by theperipheral expansion and contraction, and thus make these forceseffective in producing the transverse movement of the frusto-conicalsection 11. By

giving this stiffening ring the proper value of stiffness with respectto its mass, it is possible to exercise control-over the part of thefrequency scale at which the pumping action of the frustoconical sectionwill be made effective.

The modification of the invention shown in Fig. 4 includes a stationarysupporting wall 23 in the form of a truncated cone which is mounted atits small and in the annular member 24 in any suitable manner. Since themass of this stationary wall is unimportant, it may be made entirely ofmetal, heavy cardboard or the like. The peripheral support for the soundradiator comprises aring 25 of light flexible material, such asduralumin or light stifi paper, which as shown may be made integral withthe stationary wall 23 or may be attached thereto in any suitablemanner. The ring 25 is transversely slotted to provide a plurality oftongues 26 which offer very slight resistance to the radially actingforces developed in the conical diaphragm l0, and at the sametime offera large resistance to transverse movement. The common periphery of theconical diaphragm 10 and the frusto-coni cal section 11 is seated in theupturned ends 2'7 of the flexible'tongues 26.

In this construction, openings are provided on both sides of the conicaldiaphragm at 12 and 24, respectively, the frusto-conical section 11 and'the stationary wall 23 closed air chambers on phragm. The air enclosedin these chambers is found to add air mass reactance to the diaphragm,which tends to" lower its fundamental frequency and hence improves theperformance in the low frequency range. Since it is desired in thisconstruction to'secure the maximum air transformer action on caldiaphragm, a ribbon of light cloth a 28 is pasted over the peripheralsupporting ring 25 in such a way as to cover the slots formed by thetongues 26 without preventing the tongues from yielding to the radialmovements of the diaphragm. The cloth covering 28 is to prevent airleakage through the peripheral supporting ring.

providing partially en-' Fig. 5 shows a modification of the double airchamber construction of Fig. 4. The'edges of the-section 11 and the wall23 are bent outwardlyto form flanges 29. The periphery of the diaphragmi0 is supported between loosely packed both sides-of the dia-- bothsurfaces of the coni 1.- A sound reproducer comprising a large directacting diaphragm having a configuration to impart to it inherentstiffness from the center outwardly, and means for constraining the edgeof said diaphragm with respect to transverse movements, said meansexercising substantially no constraint to movements of said diaphragmedge in a radial direction.

2. A sound reproducer comprising a conical diaphragm driven at the apex,and means for constraining said diaphragm in a direction perpendicularto the plane of its base the periphery of which may move substantiallyfreely in a direction along said plane.

3. A sound reproducer comprising a conical diaphragm driven at the apex,and a support for the base of said diaphragm including a plurality offlexible members maintaining said base in one plane, said membersimposing substantially no restraint to the expansion and contraction ofthe base in response to sound vibrations.

4. A sound reproducer comprising a conical diaphragm driven at the apex,and a support for the base of said diaphragm including a plurality ofcircularly disposed members which are flexible only in a direction ofthe plane of said base.

5. A sound reproducer comprising a conical diaphragm and afrusto-conical section having their bases joined together to form acommon periphery, and means for constraining said periphery with respectto transverse movement, said means exercising substantially no restraintto the free movement of said periphery in a radial direction.

6. A sound reproducer comprising a conical diaphragm and afrusto-conical section bound together along an edge, and a support forsaid bound edge including a plurality of flexible membersmaintainingsaid edge in one plane, said support exercising substantially norestraint to the expansion and contraction of said bound edge inresponse to sound vibrations.

'1. A sound reproducer comprising a conical diaphragm driven at theapex, a frusto-conical section having its base joined to diaphragm, anda flexible support for said diaphragm and said frusto-conical section,said support constraining said joined bases to movement in one plane tocause said frusto-conical section to move in an opposite direction tothat of said diathe base of said riphery, means for driving said conicaldiaphragm at the apex, and a support for said periphery including aplurality of circularly disposed members which are inherently flexiblein a direction of the plane of said periphery and are inherently rigidin a direction perpendicular to the plane of said periphery.

9. A sound reproducer comprising a large direct acting diaphragm, andmeans providing a partially enclosed air chamber on both sides of saiddiaphragm, the area of the opening of each chamher being smaller thanthe radiating area of the diaphragm.

10. A sound reproducer comprising a conical diaphragm, a frusto-conicalsupportformingi a partially enclosed air chamber on one side of saiddiaphragm, and a frusto-conical section forming a partially enclosed airchamber on the other side of said diaphragm;-

11. A sound reproducer comprising a conical diaphragm driven at theapex, a frusto-conical section forming, a partially enclosed air chamberon one side of said diaphragm, a stationary frusto-conical supportforming a partially enclosed air chamber on the other side of saiddiaphragm, and means for flexibly connecting said diaphragm andfrusto-conical section to said sup port. I

121A sound reproducer comprising a conical diaphragm driven at the apex,a frusto-conical section attached to and forming a partially enclosedair chamber on one side of said diaphragm, a stationary frusto-conicalsupport forming a partially enclosed air chamber on the other side ofsaid diaphragm, and means for connecting said diaphragm andfrusto-conic'al section to said support including a plurality ofcircularly disposed memberswhich are inherently flexible only in adirectionof the plane of the base of said diaphragm.

the plane of said edge, said means imposing substantially no restraintto the movementof said edge in the plane of the periphery. 1

14. A sound reproducer comprising a large direct acting diaphragm havinga configuration to impart to it inherent stiffness from the centeroutwardly, and means to allow of a minimum of movement of s the edge ofsaid diaphragm in a direction transverse to the plane of its base, saidmember, an actuating said housing,

element, and a p 3 means offering a minimum of restraint to the movementof said edge in the plane of the said diaphragms base.

15. A loud speaker comprising a supporting member, a housing carried bysaid supporting device positioned within a cone shaped diaphragmactuated by said actuating device, and a horn carried by said housingand conforming to the. shape of said cone shaped diaphragm for providinga chamber between the exterior surface of said cone shaped diaphragm andthe interior wall of said horn.

16. A sound reproducing device comprising a large size diaphragminherently weakening the higher harmonics, and an air obstruction wallopposite said diaphragm to form an outwardly flaring air chamber foraccentuation of said high- ,er harmonics.

17. A loud-speaking device comprising a large sizecone-shaped diaphragm,and an air obstruction wall opposite said diaphragm to form an outwardlyflaring sound air chamber.

18. In combination with an electric loudspeaker, a loudspeaker actuatingelement, a coneshaped sound producing surface operated by said soundamplifying chamber associated. with said cone-shaped surface to form atapering opening towards the apex of said cone.

19. A loud speaker including a base, a strut extending from the base, adiaphragm mounting means supported by the strut, a diaphragm mounted onthe mounting means, and asound reproducing unit connected to thediaphragm for applying vibrations thereon, and means forming aloadingchamber for applying an air column load on the diaphragm. V

20. A sound reproducer comprising a direct acting diaphragm, and meansincluding a frustoconical member providing a partially enclosed airchamber on each side of said diaphragm, the larger baseof said memberabutting on the periphery of said diaphragm.

EDWIN I-I. SMYTHE.

